Charge limited high voltage switch circuits

Abstract

High voltage switches are configured with a junction transistor driven with a transformer coupled AC drive signal in the common base configuration or driven by a capacitor coupled charge pump. The high voltage switches may be configured as half wave or full wave switches wherein the junction transistor is driven during one or both half cycles of the AC drive signal. Bipolar switches that can stand off high DC voltage of either polarity, or that can stand off high AC voltage, are configured from two junction transistors with their bases connected and their emitters connected. These switches may also be driven in full wave or half wave mode, by a transformer or by single or dual capacitive charge pumps. Either NPN or PNP transistors may be used. Example drive circuits, which can be constructed as low voltage integrated circuits, are given for all of the switch types.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority from U.S. Provisional Patent Application 60 / 794,500 filed Apr. 24, 2006 entitled “Charge Limited High Voltage Switch Circuits”, the entire contents of which is incorporated herein by reference.TECHNICAL FIELD[0002]The present invention relates to high voltage electronic switches, and in particular, to high voltage switches employing junction transistors.BACKGROUND INFORMATION[0003]Electronic switches represent a very great part of the advance in electronics as a whole in the last few decades, replacing metallic contacts in virtually all fast applications. All Pulse Width Modulation [PWM] power circuitry depends on fast electronic switching. At low to moderate supply voltages, typically below 50V, MOSFETs are extremely effective switches. Toward the high end of this range, however, MOSFET based high side switch drivers are problematic and expensive. At 100V and above, MOSFETs usually require 10V of drive vo...

AI Technical Summary

Benefits of technology

[0005]The present invention envisions several ways of driving emitters in common base junction transistor stages that eliminate the need for separate high side and low side driver stages and enables drive directly from ordinary low voltage integrated circuits.

Problems solved by technology

Toward the high end of this range, however, MOSFET based high side switch drivers are problematic and expensive.

Both of these restrictions limit the transconductance [Gm] of the device.

Unfortunately, prior art driving means utilizing junction transistors have typically been arranged in a common emitter mode, often requiring separate high side or low side driver stages, and are difficult to drive directly from ordinary low voltage integrated circuits.

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